1. Technical Field
The subject matter described herein relates in general to a catalyst composition for isomerization of paraffins comprising of at least one heteropoly acid and reduced graphene oxide. The invention also relates to a process for preparation of a catalyst composition for isomerization of paraffins. The invention further relates to a process for isomerization of paraffins using the catalytic composition.
2. Related Art
Graphene is a two-dimensional pure carbon sheet possessing remarkable strength, electrical and thermal conductivity. One atom thick graphene sheet may be obtained by chemical exfoliation of graphite by Hummer's Method or by chemical vapor deposition under controlled conditions. However graphene cannot be utilized as such because it is an unreactive and inert material without proper functionalization, on the other hand, reduced graphene oxide (rGO) is a reduced form of oxygenated graphene and is expected to be a very promising material to be used as a support in catalytic transformations owing to its remarkable properties such as high surface area, mechanical strength and thermal conductivity along with the potential to be utilized in the form of various nano and meso scale structures. The reduced graphene oxide sheets thus, can be functionalized and used as support for different organic transformations (Guerra et al., Appl. Catal A: Gen 2013; 468:474 467).
Phosphomolybdic acid (PMA) belongs to the class of materials called heteropoly acids which exist in one of the Keggin, Dawson or other structural forms. It is a highly acidic material and exhibits some very interesting properties such as pseudo-liquid behavior (Kozhevnikov IV. Chem Rev 1998; 98:198-171.), utility as catalyst in both homogeneous and heterogeneous phase (Kozhevnikov IV. J. Mol. Catal A: Chem 2007; 262:92-86.), low temperature activity and reversible structure evolution in the presence of water up to certain temperatures (Micek-Ilnicka A. J Mol. Catal A: Chem 2009; 308:14-1.) However PMA is a bulk material with very low surface area (<5 m2/g) and low mechanical strength thereby limiting its applications. Recently, high resolution in situ and ex situ TEM studies have indicated that the crystallite size of platinum governs the nature of carbon deposited over the support as graphene sheets or carbon nanotubes (Peng et al., J. Catal. 2012; 286:29-22).
Monofunctional hybrid materials based on Keggin-type heteropolyacids supported on mesostructured silica were used in isomerization of n-hexane. The heteropolyacids, namely H3PW12O40 or H4SiW12O40, were immobilized onto SBA-15 type silica by incipient wetness impregnation. The resulting catalysts were thoroughly characterized by N2 adsorption-desorption isotherms, XRD, 31P NMR, TGA and FT-IR. These hybrid materials were active for the gas-phase isomerization of n-hexane (Pinto et al., Applied Catalysis A: General 483 (2014): 103-109.). In another study, isomerization of n-butane in the presence of hydrogen catalyzed by a bifunctional catalyst consisting of Pt and Cs2.5H0.5PW12O40 was examined mostly at 573 K. (Kyutae, et al., Journal of Molecular Catalysis A: Chemical 115.3 (1997): 449-455.)
Jin et al. reported a series of Ni—CsxH3-xPW12O40/SiO2 catalysts which were prepared by direct synthesis method and characterized by BET, XRD, in situ XRD, FT-IR, NH3-TPD, H2-TPR, and H2-TPD. The catalytic performance of the catalysts for the hydrocracking of n-decane with various concentrations of thiophene and pyridine was studied. (Jin, Hao, et al., Fuel 112 (2013): 134-139.)
In another study, Cs-exchanged phosphotungstic acids (CsxH3-xPW12O40, x=1-3) were examined as a catalyst for the hydrocracking of extra-heavy oil (vacuum residue, API gravity=2.3°). (Eom, Hee-Jun, et al., Fuel 126 (2014): 263-270.)